The fall is relative of course; even with an eight-point drop, spam continued still accounted for a staggering 72 percent of all email during the year, equivalent to tens of trillions of messages moving uselessly and malevolently across the Internet every year.

The drop was consistent throughout the year, falling month-on-month, eventually dipping below the 70 percent threshold in the final three months of the year, Kaspersky said.

What is clear is that the exact percentage of spam sent to a user or network varies by country and region, with Asia now accounting for a disproportionate level of activity.

In terms of distribution, China heads the table with one in five of all spam messages sent, ahead of the US with 15.6 percent; Latin America and Europe both dropped. Asia as a whole now accounts for half of all jump email.

Malicious attachments were down slightly to 3.4 percent, although this does not include those with embedded links.

According to Kaspersky, the unprecedented fall can be explained by the gradual improvement in filtering.

Arguably, the disruption of botnets - the platform used to send most spam - has probably had a larger effect, with the downing of several large distribution networks coinciding with the start of spam's decline in 2010.

It could also be that there are better ways to make money from cybercrime, not least by infiltrating social media.

"This drop is the result of a gradual departure of advertisers from spam to other, more convenient and legal means of promoting goods and services," said Kaspersky Lab's Darya Gudkova.

"However, that doesn't mean spam is headed the way of the dodo anytime soon. Malicious spam, fraud, and advertising of illegal goods cannot simply or easily migrate to legal platforms, due to their own inherently criminal nature. We expect that the decline in spam volumes in 2013 will be negligible at best," he said.

Doubtless, some will disagree with Kaspersky's numbers, which only reflect what its customers see. But they do chime with what other security companies have been saying for two years.